1. Field of the Invention
This invention relates to a method and apparatus for marking the location of buried objects. More particularly, this invention relates to barhole drivers or plunger bars for creating holes from above ground to an underground location proximate a buried object and for marking the location of the buried object.
2. Description of Related Art
In-ground pipelines are used for a variety of purposes. For example, and without an unnecessary limitation, in-ground pipelines are used extensively in the transmission of various materials between selected points for locations. Natural gas is one example of a material frequently transmitted via in-ground pipelines.
It is known that damage to in-ground pipelines can occur directly as a result of acts of nature such as earthquakes and landslides. The damage resulting from in-ground pipelines as a result of the occurrence of such events typically occurs on a sufficiently large scale such that multiple pipe joints are affected and detection of the occurrence of such damage is relatively easy. However, pipeline damage can also occur due to the activity of a third-party, i.e. a party other than the owner or operator of the pipeline. Such damage is known as “third-party damage.” When the damage due to an act of a third party causes an immediate rupture of a pipe, little can be done via on-line monitoring to prevent an ensuing incident. However, many third-party contacts with pipelines may cause damage that does not result in an immediate pipeline failure but rather cause damage that may, with time, lead to a pipe failure such as in the form of a leak or a catastrophic rupture. The occurrence of such third-party contact and the effective detection thereof has proven to be a persistent problem. While sounds associated with contact with the pipeline can be transmitted through the pipeline and detected at substantial distances from the point of contact via highly sensitive acoustic sensors, the high sensitivity of such sensors can generate a significant number of false alarms arising from sources other than by contact with the pipeline. For example, sources such as passing vehicles and weather conditions, such as thunder and rain, can produce to a normal sound detection and monitoring method and system.
In view of the consequences of the failure of an in-ground pipeline due to third-party contact, particularly when coupled with the extensive construction related with urban expansion and encroachment of the right-of-way commonly associated with many of such in-ground pipelines, the importance of preventing such third-party contacts is apparent. Typically, the primary approach to preventing such third-party contact has been to mark the location of the in-ground pipeline through the use of above-ground means visible to excavators. Current methods of marking an excavation site, which include the use of small flags or paint, are applied at the surface above the location of the in-ground pipeline. However, such markings frequently become lost when excavation begins. Other methods of marking an excavation site include, for example, the placement of RFID devices in the ground proximate the in-ground pipeline, which devices are detectable from above ground. Disadvantageously, current methods for the placement of RFID devices in the ground involve excavation or drilling. And, finally, shifting in the ground caused by ground disturbances, such as earthquakes, may result in a relocation of the marking means relative to the in-ground pipeline as a result of which the marking means is no longer indicative of the location of the in-ground pipeline.
Barhole drivers, also known as plunger bars, are used to create holes in soil, concrete, and the like. The most common use of plunger bars is for making holes in the ground in order to detect and determine the location of gas leaks from natural gas utility pipelines. Conventional plunger bars comprise three basic components, a solid rod having a tip for promoting ground penetration and a drive means connected with the solid rod for driving the tip and the rod into the ground. However, when the plunger bar is removed from the ground, the hole created by the plunger bar quickly closes up after the bar is withdrawn.